Stabilization of motor fuels



Patented Dec. 23, 1947 Paul L. De Verter, Baytown, Tex., asslgnor to Standard Oil Development Company, a corporation of Delaware N Drawing. Application November 13, 1942. Serial No. 465,459

Claims. 1

This invention relates to motor fuel compositions stabilized against deterioration during storage, and more particularly to such stabilization of motor fuels which contain lead alkyl antiknock agents.

While standing in storage, some gasoline components are slowly oxidized to objectionable materials known as gums, which cause engine troubles. To determine the stability of gasolines against gum formation, there have been devised laboratory tests which are correlated to the effects of storage. These tests have been recognized to have the ability of satisfactorily evaluating storage stability for a period of two to three years, or longer, and accordingly, have been incorporated into exacting military as well as non-v military specifications.

In substance, the Army-Navy "accelerated gum test requires that a sample of gasoline'having a piece of steel immersed in it be contacted with oxygen under 100 lbs/sq. in. pressure at 212 F. for 5 hours without causing the formation-of more than a tolerated gum content. In order to pass'strict specifications, the gum content (corrected or uncorrected, depending on the presence of tetraethyl lead) must not exceed 6 mgs\/ 100 ml. of the fuel. These conditions are the equivalent of from about 18 months to two years of storage.

The requirements of the accelerated gum test" are rather severe, and although they are frequently met by unleaded straight run naphthas, there are very few gasolines important in aviation fuels which can pass these testswhen containing tetraethyl lead. Only some of the very purest synthetic gasoline hydrocarbons are satisfactorily stable both with and without the addition of the tetraethyl lead anti-knock agent. Due to the increased demand for leaded aviation fuels, it has chloride. About 0.2 lb. of zinc chloride in 1000 gallons of gasoline is sufllcient to accomplish the desired stabilization. However, the minimum requirement for some stocks may be greater or less than this amount. The minimum amount of the metal halide inhibitor required for any fuel to pass the accelerated gum test can be determined by a few simple tests, and this minimum amount, which is generally" at least 0.1 lb. per 1000 gallons of fuel, is suflicient to stabilize the leaded gasoline for a considerable period of time while in storage, that is, for a period of about two years of dark storage. By increasing the amount somewhat above the minimum, the extent of stabilization is also increased up to a. certain degree, but it is preferred to use as small an amount of the inhibitor as is necessary, and accordingly, in using zinc chloride and similarly effective metal halide inhibitors, concentrations of about 0.2.to 0.6 lb. per 1000 gallons of fuel were found satisfactory. In such small concentrations, these inhibitors have no detrimental eflect on the quality of the gasoline, such as might be detected by inspection tests for anti-knock value, copper dish gum, copper dish corrosion, the reaction test, and acidity of residue after distillation. The exact amount 1 of stabilizer to be used may also be varied slightly become necessary toemploy stabilizing inhibitors in the fuels which otherwise could not meet stability specifications. At present there are known to be several effective organic inhibitors which have gained approval for use in leaded aviation fuels, but there have been considerable efforts to determine other factors of stabilization and find other inhibitors which function to prevent oxidation of leaded aviation fuels during storage 'or in the accelerated gum test of the fuel specifications.

certain inorganic compounds represented particularly by halides of metals in groups II to IV of the Mendeleef Periodic Table are eflicient in- The invention is based upon the discovery that according to the, amount of lead alkyl anti-knock agent used, as will be discussed later.

Although zinc chloride has been indicated as the preferred metal halide to be used as inhibitor or stabilizer according to this invention, other metal halides may be used such as stannous chloride, SnCla, stannic chloride, SnCh, magnesium chloride, MgClz, and aluminum hloride, AlCh. Soldering fluxes comprising metal chlorides or organo-metallic chlorides alone or with hydrochloric acid may be employed as inhibiting agents. For satisfactory stabilization of Sasolines with the aforesaid inhibiting agents, the soluble halide.

content of the gasoline, when expressed as dry HCl, should be in the order of 0.05 to 0.5 pound per 1000 gallons. Although chlorine has been thus far indicated as the halogen to be present in the halide, other halogens may also be used such as bromine, iodine, and fluorine. Broadly, the halide to be used as inhibitor might be expressed by the general formula MX, where M represents a metal selected from groups 11 to IV of the periodic table, preferably a metal in the righthand column of those groups, and X represents one or more halogen atoms according to the valency of M. Mixtures of. these various halides may also be used.

The inhibitor in, the preferred small ccncenhalide to prevent any preci 'applied to motor tratlons may be readily. incorporated into a hydrocarbon gasoline. In adding the inhibitor in any concentration, and particularly higher concentrations, it is preferred to use a solubilizing agent which is readily miscible with the hydrocarbons and which has no detrimental effect on the quality of the fuel, e. g., low boiling alcohols, e. g., ethyl alcohol, isopropyl alcohol, etc., ketones. e. g., acetone, methyl ethyl ketone, methyl isobutyl ketone, and anti-knock ethers, e. g., di-iscpropyl ether, isopropyl tertiary butyl ether, or the like. For example, zinc chloride may be dissolved in ethyl alcohol in a concentration of 4 lbs./gallon, then of a gallon of this solution may be added to each thousand gallons of gasoline to give it a zinc chloride content of 0.2 lb./1000 gallons. As an extra precaution, a trace of hydrochloric acid or hydrogen chloride may be placed in the alcoholic solution of the metal pitation from occur- 20 ring. Of course, if desired, a smaller concentration of the metal halide in alcohol may be used, such as 1 lb. or ,5 lb.'of ,62 lb. of the stabilizer per gallon of alcohol.

From extensive experience. it has been found that a slight precipitate, white, yellow. or brown, is formed. or the gasoline sampleis slightly cloudy after oxidation when the total lead and gum precipitated exceeds man/ 0 on analysis. these precipitates show the presence .of lead oxides, indicating a breakdown of the tetraethyl lead. In some of the gasoline hydrocarbons this breakdown occurs more readily than in others. In alkylates, cracked gasolines, solvent extract gasolines, and some hydrogenated polymer gasolines. the oxidation tendency is quite pronounced, and the invention is particularly applicable for lead dimethyl diethyl, lead monomethyl triethyl, or even lead alkyls containing higher alkyl groups than ethyl. The invention may also be applied to motor fuels containing mixtures of two or more different lead alkyl anti-knock agents. The amount of the lead alkyl agent used in the motor fuel may vary accordnock properties, generally expressed as octane number, desired in the finished fuel blend. but normally will range from about 0.5 to 3 cc. of lead alkyl per gallon of fuel, although considerably more may be used since Government specifications now permit 4 cc. per gallon at least for said military purposes. If only 1 cc. of T. E. L. (tetraethyl lead) is used per gallon of fuel, 0.1 lb. of zinc chloride per 1,000 gals. of fuel will normally suffice for stabilization, and on the other hand, with larger than normal amounts of T, E. L., e. g., 4 cc. per gallon of fuel. 0.2 to 0.4 lb. of zinc chloride per 1,000 gals. of fuel will usually be required.

The efllcacy of the inorganic inhibitors was determined through the recognized accelerated gum tests and through actual storage tests. As a result of these tests, it was concluded that the inorganic inhibitors make feasible a practicable stabilization of the fuels commensurate with the effectiveness of well-known organic inhibitors.

In Table l is listed accelerated gum test data obtained on several difierent samples of avialion fuels containing 3.0 cc. of T. E, L. (tetraethyl lead) per gallon with varied concentrations of zinc chloride as the inhibitor. In blending the zinc chloride with the hydrocarbon fuel, a small use in stabilizing such fuels, although broadly it amount of ethyl alcohol was used to dissolve the is intended to be applied to any leaded motor zinc "chloride, and it was found that the ethyl fuel which tends to discolor and develop a prealcohol by itself had no inhibiting eflect.

Table 1 v Accelerated Gum Test TypeofProduct I ZnOlg Added contains 3.0 T. E. L. cc. Lbs. 1000 [gal I gal. Precipltate a 35 Lead Gum 1 100 Octane Aviation Fuel A-l..- o Hvy. Brown.. 27. 9 2 d 3.0 None 7.3 3...- 100 Octane AviationFuelA-2.. 0 Hvy. Browm- 43.9 4 do 3.0 None 7.5 s..--.- Pecos Aviation Fuel B-l 0 ace 6 do 0.2 on 4.3 7 m. 0.4 3.3 1.0 4.5 o 25.2 do 0.3 one 6.0 0 Hvy. Brown.- 31. 4 12 do Alcohoi -do.. 27.9 i Alky l ato runes 3 fi d'aaa" 6'5 1 15 do 0.05 Y. o-. 40.9 16 do' 0. l0 Sit. Bram-.- ll. 1

2 d vedinalcohol-ixmeentl'ation 1 lb. ZnCh no alcohol. f ,j

no], N used,theequivalent i l i what o uldbeadded throu' 1 No Z1101: used-2.4 gal. alcohol ZnCh reagent.

regardless of .the source which the fuel base The above tests show thatfva'zious amounts ranging from 0.1 to 3.0 lbs. of ainc chloride per 1000 gallons of fuel were effective or entirely prevented formation of any precipitate and it substantially reduced the gum andflead deposits during the accelerated gum test. Test No. 12 shows that the amount of alcohol, used as solubilizer for the zinc chloride, does not per se have any substantial effect in reducing either the formation of a heavy brown precipitate or in reducing the amount of lead and gum deposits in the accelerated gum test, so that it is clear that the addition of zinc chloride is responsible for the surprisingly good results obtained in the aesaoss or. as shown in tests 26-28, washing the fuel with concentrated hydrochloric acid in the proportion of 1.0 gallon of acid per 1000 gallons of oil was required to obtain satisfactory stabilization. With tests in which zinc chloride was used. this same alkylate fuel, 06 lb. of zinc chloride per Another series of-tests, the results'Of which are 1000'gallons of fuel was required for stabilization. shown in Table 2 herebelow, were made to ascer- Similarly, as shown in tests 32-37, 0.6 to 1.0 lb. tam whether the addition of zinc chloride w uld of stannous chloride, stannic chloride, magnesium have any detrim nt l eff c On the q y of the chloride, and aluminum chloride likewise profuel as indicated by octane number, copper dish m duced satisfactory stabilization. Accordingto test gum, copper dish corrosion, reaction test, and No. 38, washing an alkylate fuel with a'commeracidity of residue after distillation. cial liquid soldering flux which contained'a sub- Table 2 1 Cu Acidity z 01, 01: D h it. ar 33;;

17 100 Oct. Base (unleaded) 0 86.1 1.2 01K Negative None. 18 ..do 0.2 80.1 1.0 0. K Do. 100 Oct.Base-l- 3.0ec.i. E.L 0 100 1.7 0. Km... ..c 0. Do. 20 .40 0.2 100 1.3 0. K .130. These tests show that the use of 0.2 lb. of zinc stantial proportion of zinc chloride and some hychloride per 1000 gallons of fuel .(which as shown drochloric acids using one gallon of flux per 1000 in Table 1 was sufflcient to prevent'the deterioragallons of fuel was substantially as effective as a tion during storage as indicated by the accelerated similar amount of straight hydrochloric acid. On gum test) had no deleterious effect on the octane the other hand, although not shown in the test, number or on any of the other characteristics dewashing an alkylate fuel with a similar amount of termined in this series of tests. concentrated sulfuric acid. i. e., one gallon of acid Another series of tests was made to compare 3" per 1000 gallons of fuel, did not prevent the the effect of zinc chloride in various coneentraformation of a precipitate and did not prevent the tions on two other fuel base stocks to which 3 cc. formation of a substantial lead deposit in the acof T. E. L. per gallon had been added, and. to celerated gum test. .The metal chlorides are predetermine the effectiveness of various inorganic ferred to hydrochloric acid from the point of view halides other than'zinc chloride. The results of of causing less corrosion of metals, and of all of these tests are shown in the accompanying the halides used in this series of tests the zinc Table 3. chloride is the most practical.

Table 3 Accelerated Gum Test Test sample itttiiliif" Lad Precipitate and Lead Gum Gum 37.0 26.8 10.2 1 0.2 ZnCh s1. Brow 18.8 1.2 0.0 \Peoos Aviation Fuel 13. \OA Z1101," None.... 6.7 3. 7 3.0 1.0 u .do 0.2 3.4 2.8 0.5 do 0.9 4.1 as 0 Hy. Brown '30. 6 25.0 5. 6 0.5 None s1. Turbid) 10.2 1.0 N 4.2 0.4 znch..... 24.0 16.8 7.2 0.0 znoh 1.0 1.0 znch as Alkylate o. 0.6SnC1: do. 1.0 Nil 7.0 l 1.0 SnCh... None s1. Turbid) 4.0 Nil 4.0 0.6 511014 None 7.2 Nil 7.2 L0 SnOl4 Trace White. 1.7 Nil 1.7 .e MgChL. 2.0 Nil 2.0 1.0 A1013 1.5 Nil 1.5 1 Gal. Soldering Flux (In N 4.2 alcohol)? a l Gallons of 38% 01 this acid One gallon aqueous hydrochloric acid agitated with 1000 gallons oi gasoline; most (estimated as being at least asoline before testing. Liqu d) soldering flux. comprising HCl and 211011, agitated with 1000 gallons of gasoline; most of this flux (estimated as being at least settled out and was removed from the gasoline before ions or fuel. On the other hand with alkylate fuel Some preliminary storage tests were also made 05 in which octane gasoline containing 3 cc. of

T. E. L. was stored in brown glass bottles for thirty days with and without small iron strips which apparently acted as oxidation catalysts in increasing the severity of the deterioration. The

following Table 4'shows the results of these tests before and after thirty days storage,.tests 39-41 being without any inhibitor and tests 42-44 being made with 0.4 lb. of zinc chloride per 1000 gallons of fuel under test conditions comparable to those used in tests 39-41.

I cate that 0.4 lb.

- of 100 octane gasoline (containing 3 cc. of tetraalaaoas Table Acacia-need Gum 'r N 8 lo c m est 0. amp on no! em Precipitata 5" Pb Gum 5 Brown Bottle Heavy Brown 2a: 14. a 12. 1 }l Oct. Gasoline 0 d0 so ..do m 18.8 11.7 Brown Bottle-l-Fe Siripe.. 00 -do. 74.2 57.2 17.0 Brown Bottle 0 Nono 3.0 -i P00 Oct. Glsoline... .4 ZnCl; 0 30 do 8.1 .I. Brown Bottle-l-Fe Strips-. 30 None (Slightly Turbid)... 8.8

The results shown in the above Table 4 indiof zinc chloride per 1000 gallons ethyl lead per gallon) was sufficient to prevent brown precipitate formation and to prevent lead and gum deposits during the accelerated gum test, not only when tested immediately before storage but also when tested after thirtydays storage, either in the glass bottle without iron strips or in the bottle with iron strips. This is quite remarkable since the presence of the iron strips. as shown in test 41, very greatly increased the amount of lead and gum deposits in the accelerated gum test. In all three instances the use of the zinc and 3.3.

Although no comparable test results are available on a gasoline containing tetraethyl lead, two tests were made to determine the octane number after two years storage of an unleaded fuel base stock with and without zinc chloride. 7 These tests showed that without the zinc chloride the fuel had an octane number of 83.0, whereas with 0.2 lb. of zinc chloride per gallon of fuel, the octane number was 84.0, thus indicating chloride had a partial stabilizing effect on the gasoline base stock even in the absence of tetraethyl lead. The octane number of this gasoline base stock before the two years storage was probin view of the re-' markable effectiveness of the zinc chloride as shown in Tables age of an uninhibited fuel containing tetraethyl lead would be very much lower than the octane chloride reduced the lead and gum deposits frombetween 26-74 down to between 3.0 30

number of a similar fuel containing zinc chloride.

It is not intended that this invention be limited to the specific examples which have been iven necessarily by any theory of the operation of the invention, which is not clearly understood, but only by the appended claims in which it is intended to claim all novelty 00 as to the mechanism inherent in the invention as well as all modincations coming within the scope and spirit of the invention. I claim:

1. A motor fuel comprising a maior proportion of gasoline, about 0.5 to 0.0 cc. of tetraethyl lead per gallon of gasoline, and about 0.1 to 1.0 lb. of zinc chloride per 1000 gallons of fuel.

2. Fuel according to claim 1 also containing a small amount of organiccompound selected from the group consisting of low boiling alcohols, ethers and ketones as solubfiizerfor the zinc chloride in the gasoline.

4. A motor fuel comprising of a gasoline base stock having her at least as high as 80, a tetraethyl lead said gasoline base stock up to 100, and about 0.2 to 0. lbs.

of zinc chloride per 1000 gallons of fuel.

PAUL L. DE VERTER.

REFERENCES CITED i The following references are of ecord in the file of this patent:

NITED STATES PATENTS Number I Name Date 2,067,331 Michel Jan-12, 193'! 2,115,781 Morrell May 3, 193a FOREIGN PATENTS Number Country Date Great Britain Jan. 5. 1037 

